Provided by: libmath-gsl-perl_0.43-4_amd64 
NAME
Math::GSL::Const - Constants
SYNOPSIS
use Math::GSL::Const qw/:all/;
print "The Euler-Mascheroni Constant is $M_EULER\n";
There are many constants in this module, which are split into six subcategories a.k.a
tags:
TAGS
• cgs
• $GSL_CONST_CGS_SPEED_OF_LIGHT
• $GSL_CONST_CGS_GRAVITATIONAL_CONSTANT
• $GSL_CONST_CGS_PLANCKS_CONSTANT_H
• $GSL_CONST_CGS_PLANCKS_CONSTANT_HBAR
• $GSL_CONST_CGS_ASTRONOMICAL_UNIT
• $GSL_CONST_CGS_LIGHT_YEAR
• $GSL_CONST_CGS_PARSEC
• $GSL_CONST_CGS_GRAV_ACCEL
• $GSL_CONST_CGS_ELECTRON_VOLT
• $GSL_CONST_CGS_MASS_ELECTRON
• $GSL_CONST_CGS_MASS_MUON
• $GSL_CONST_CGS_MASS_PROTON
• $GSL_CONST_CGS_MASS_NEUTRON
• $GSL_CONST_CGS_RYDBERG
• $GSL_CONST_CGS_BOLTZMANN
• $GSL_CONST_CGS_BOHR_MAGNETON
• $GSL_CONST_CGS_NUCLEAR_MAGNETON
• $GSL_CONST_CGS_ELECTRON_MAGNETIC_MOMENT
• $GSL_CONST_CGS_PROTON_MAGNETIC_MOMENT
• $GSL_CONST_CGS_MOLAR_GAS
• $GSL_CONST_CGS_STANDARD_GAS_VOLUME
• $GSL_CONST_CGS_MINUTE
• $GSL_CONST_CGS_HOUR
• $GSL_CONST_CGS_DAY
• $GSL_CONST_CGS_WEEK
• $GSL_CONST_CGS_INCH
• $GSL_CONST_CGS_FOOT
• $GSL_CONST_CGS_YARD
• $GSL_CONST_CGS_MILE
• $GSL_CONST_CGS_NAUTICAL_MILE
• $GSL_CONST_CGS_FATHOM
• $GSL_CONST_CGS_MIL
• $GSL_CONST_CGS_POINT
• $GSL_CONST_CGS_TEXPOINT
• $GSL_CONST_CGS_MICRON
• $GSL_CONST_CGS_ANGSTROM
• $GSL_CONST_CGS_HECTARE
• $GSL_CONST_CGS_ACRE
• $GSL_CONST_CGS_BARN
• $GSL_CONST_CGS_LITER
• $GSL_CONST_CGS_US_GALLON
• $GSL_CONST_CGS_QUART
• $GSL_CONST_CGS_PINT
• $GSL_CONST_CGS_CUP
• $GSL_CONST_CGS_FLUID_OUNCE
• $GSL_CONST_CGS_TABLESPOON
• $GSL_CONST_CGS_TEASPOON
• $GSL_CONST_CGS_CANADIAN_GALLON
• $GSL_CONST_CGS_UK_GALLON
• $GSL_CONST_CGS_MILES_PER_HOUR
• $GSL_CONST_CGS_KILOMETERS_PER_HOUR
• $GSL_CONST_CGS_KNOT
• $GSL_CONST_CGS_POUND_MASS
• $GSL_CONST_CGS_OUNCE_MASS
• $GSL_CONST_CGS_TON
• $GSL_CONST_CGS_METRIC_TON
• $GSL_CONST_CGS_UK_TON
• $GSL_CONST_CGS_TROY_OUNCE
• $GSL_CONST_CGS_CARAT
• $GSL_CONST_CGS_UNIFIED_ATOMIC_MASS
• $GSL_CONST_CGS_GRAM_FORCE
• $GSL_CONST_CGS_POUND_FORCE
• $GSL_CONST_CGS_KILOPOUND_FORCE
• $GSL_CONST_CGS_POUNDAL
• $GSL_CONST_CGS_CALORIE
• $GSL_CONST_CGS_BTU
• $GSL_CONST_CGS_THERM
• $GSL_CONST_CGS_HORSEPOWER
• $GSL_CONST_CGS_BAR
• $GSL_CONST_CGS_STD_ATMOSPHERE
• $GSL_CONST_CGS_TORR
• $GSL_CONST_CGS_METER_OF_MERCURY
• $GSL_CONST_CGS_INCH_OF_MERCURY
• $GSL_CONST_CGS_INCH_OF_WATER
• $GSL_CONST_CGS_PSI
• $GSL_CONST_CGS_POISE
• $GSL_CONST_CGS_STOKES
• $GSL_CONST_CGS_FARADAY
• $GSL_CONST_CGS_ELECTRON_CHARGE
• $GSL_CONST_CGS_GAUSS
• $GSL_CONST_CGS_STILB
• $GSL_CONST_CGS_LUMEN
• $GSL_CONST_CGS_LUX
• $GSL_CONST_CGS_PHOT
• $GSL_CONST_CGS_FOOTCANDLE
• $GSL_CONST_CGS_LAMBERT
• $GSL_CONST_CGS_FOOTLAMBERT
• $GSL_CONST_CGS_CURIE
• $GSL_CONST_CGS_ROENTGEN
• $GSL_CONST_CGS_RAD
• $GSL_CONST_CGS_SOLAR_MASS
• $GSL_CONST_CGS_BOHR_RADIUS
• $GSL_CONST_CGS_NEWTON
• $GSL_CONST_CGS_DYNE
• $GSL_CONST_CGS_JOULE
• $GSL_CONST_CGS_ERG
• $GSL_CONST_CGS_STEFAN_BOLTZMANN_CONSTANT
• $GSL_CONST_CGS_THOMSON_CROSS_SECTION
• cgsm - CGSM system (centimeters, grams, seconds, gauss)
• $GSL_CONST_CGSM_SPEED_OF_LIGHT
• $GSL_CONST_CGSM_GRAVITATIONAL_CONSTANT
• $GSL_CONST_CGSM_PLANCKS_CONSTANT_H
• $GSL_CONST_CGSM_PLANCKS_CONSTANT_HBAR
• $GSL_CONST_CGSM_ASTRONOMICAL_UNIT
• $GSL_CONST_CGSM_LIGHT_YEAR
• $GSL_CONST_CGSM_PARSEC
• $GSL_CONST_CGSM_GRAV_ACCEL
• $GSL_CONST_CGSM_ELECTRON_VOLT
• $GSL_CONST_CGSM_MASS_ELECTRON
• $GSL_CONST_CGSM_MASS_MUON
• $GSL_CONST_CGSM_MASS_PROTON
• $GSL_CONST_CGSM_MASS_NEUTRON
• $GSL_CONST_CGSM_RYDBERG
• $GSL_CONST_CGSM_BOLTZMANN
• $GSL_CONST_CGSM_BOHR_MAGNETON
• $GSL_CONST_CGSM_NUCLEAR_MAGNETON
• $GSL_CONST_CGSM_ELECTRON_MAGNETIC_MOMENT
• $GSL_CONST_CGSM_PROTON_MAGNETIC_MOMENT
• $GSL_CONST_CGSM_MOLAR_GAS
• $GSL_CONST_CGSM_STANDARD_GAS_VOLUME
• $GSL_CONST_CGSM_MINUTE
• $GSL_CONST_CGSM_HOUR
• $GSL_CONST_CGSM_DAY
• $GSL_CONST_CGSM_WEEK
• $GSL_CONST_CGSM_INCH
• $GSL_CONST_CGSM_FOOT
• $GSL_CONST_CGSM_YARD
• $GSL_CONST_CGSM_MILE
• $GSL_CONST_CGSM_NAUTICAL_MILE
• $GSL_CONST_CGSM_FATHOM
• $GSL_CONST_CGSM_MIL
• $GSL_CONST_CGSM_POINT
• $GSL_CONST_CGSM_TEXPOINT
• $GSL_CONST_CGSM_MICRON
• $GSL_CONST_CGSM_ANGSTROM
• $GSL_CONST_CGSM_HECTARE
• $GSL_CONST_CGSM_ACRE
• $GSL_CONST_CGSM_BARN
• $GSL_CONST_CGSM_LITER
• $GSL_CONST_CGSM_US_GALLON
• $GSL_CONST_CGSM_QUART
• $GSL_CONST_CGSM_PINT
• $GSL_CONST_CGSM_CUP
• $GSL_CONST_CGSM_FLUID_OUNCE
• $GSL_CONST_CGSM_TABLESPOON
• $GSL_CONST_CGSM_TEASPOON
• $GSL_CONST_CGSM_CANADIAN_GALLON
• $GSL_CONST_CGSM_UK_GALLON
• $GSL_CONST_CGSM_MILES_PER_HOUR
• $GSL_CONST_CGSM_KILOMETERS_PER_HOUR
• $GSL_CONST_CGSM_KNOT
• $GSL_CONST_CGSM_POUND_MASS
• $GSL_CONST_CGSM_OUNCE_MASS
• $GSL_CONST_CGSM_TON
• $GSL_CONST_CGSM_METRIC_TON
• $GSL_CONST_CGSM_UK_TON
• $GSL_CONST_CGSM_TROY_OUNCE
• $GSL_CONST_CGSM_CARAT
• $GSL_CONST_CGSM_UNIFIED_ATOMIC_MASS
• $GSL_CONST_CGSM_GRAM_FORCE
• $GSL_CONST_CGSM_POUND_FORCE
• $GSL_CONST_CGSM_KILOPOUND_FORCE
• $GSL_CONST_CGSM_POUNDAL
• $GSL_CONST_CGSM_CALORIE
• $GSL_CONST_CGSM_BTU
• $GSL_CONST_CGSM_THERM
• $GSL_CONST_CGSM_HORSEPOWER
• $GSL_CONST_CGSM_BAR
• $GSL_CONST_CGSM_STD_ATMOSPHERE
• $GSL_CONST_CGSM_TORR
• $GSL_CONST_CGSM_METER_OF_MERCURY
• $GSL_CONST_CGSM_INCH_OF_MERCURY
• $GSL_CONST_CGSM_INCH_OF_WATER
• $GSL_CONST_CGSM_PSI
• $GSL_CONST_CGSM_POISE
• $GSL_CONST_CGSM_STOKES
• $GSL_CONST_CGSM_FARADAY
• $GSL_CONST_CGSM_ELECTRON_CHARGE
• $GSL_CONST_CGSM_GAUSS
• $GSL_CONST_CGSM_STILB
• $GSL_CONST_CGSM_LUMEN
• $GSL_CONST_CGSM_LUX
• $GSL_CONST_CGSM_PHOT
• $GSL_CONST_CGSM_FOOTCANDLE
• $GSL_CONST_CGSM_LAMBERT
• $GSL_CONST_CGSM_FOOTLAMBERT
• $GSL_CONST_CGSM_CURIE
• $GSL_CONST_CGSM_ROENTGEN
• $GSL_CONST_CGSM_RAD
• $GSL_CONST_CGSM_SOLAR_MASS
• $GSL_CONST_CGSM_BOHR_RADIUS
• $GSL_CONST_CGSM_NEWTON
• $GSL_CONST_CGSM_DYNE
• $GSL_CONST_CGSM_JOULE
• $GSL_CONST_CGSM_ERG
• $GSL_CONST_CGSM_STEFAN_BOLTZMANN_CONSTANT
• $GSL_CONST_CGSM_THOMSON_CROSS_SECTION
• mks
• $GSL_CONST_MKS_SPEED_OF_LIGHT
• $GSL_CONST_MKS_GRAVITATIONAL_CONSTANT
• $GSL_CONST_MKS_PLANCKS_CONSTANT_H
• $GSL_CONST_MKS_PLANCKS_CONSTANT_HBAR
• $GSL_CONST_MKS_ASTRONOMICAL_UNIT
• $GSL_CONST_MKS_LIGHT_YEAR
• $GSL_CONST_MKS_PARSEC
• $GSL_CONST_MKS_GRAV_ACCEL
• $GSL_CONST_MKS_ELECTRON_VOLT
• $GSL_CONST_MKS_MASS_ELECTRON
• $GSL_CONST_MKS_MASS_MUON
• $GSL_CONST_MKS_MASS_PROTON
• $GSL_CONST_MKS_MASS_NEUTRON
• $GSL_CONST_MKS_RYDBERG
• $GSL_CONST_MKS_BOLTZMANN
• $GSL_CONST_MKS_BOHR_MAGNETON
• $GSL_CONST_MKS_NUCLEAR_MAGNETON
• $GSL_CONST_MKS_ELECTRON_MAGNETIC_MOMENT
• $GSL_CONST_MKS_PROTON_MAGNETIC_MOMENT
• $GSL_CONST_MKS_MOLAR_GAS
• $GSL_CONST_MKS_STANDARD_GAS_VOLUME
• $GSL_CONST_MKS_MINUTE
• $GSL_CONST_MKS_HOUR
• $GSL_CONST_MKS_DAY
• $GSL_CONST_MKS_WEEK
• $GSL_CONST_MKS_INCH
• $GSL_CONST_MKS_FOOT
• $GSL_CONST_MKS_YARD
• $GSL_CONST_MKS_MILE
• $GSL_CONST_MKS_NAUTICAL_MILE
• $GSL_CONST_MKS_FATHOM
• $GSL_CONST_MKS_MIL
• $GSL_CONST_MKS_POINT
• $GSL_CONST_MKS_TEXPOINT
• $GSL_CONST_MKS_MICRON
• $GSL_CONST_MKS_ANGSTROM
• $GSL_CONST_MKS_HECTARE
• $GSL_CONST_MKS_ACRE
• $GSL_CONST_MKS_BARN
• $GSL_CONST_MKS_LITER
• $GSL_CONST_MKS_US_GALLON
• $GSL_CONST_MKS_QUART
• $GSL_CONST_MKS_PINT
• $GSL_CONST_MKS_CUP
• $GSL_CONST_MKS_FLUID_OUNCE
• $GSL_CONST_MKS_TABLESPOON
• $GSL_CONST_MKS_TEASPOON
• $GSL_CONST_MKS_CANADIAN_GALLON
• $GSL_CONST_MKS_UK_GALLON
• $GSL_CONST_MKS_MILES_PER_HOUR
• $GSL_CONST_MKS_KILOMETERS_PER_HOUR
• $GSL_CONST_MKS_KNOT
• $GSL_CONST_MKS_POUND_MASS
• $GSL_CONST_MKS_OUNCE_MASS
• $GSL_CONST_MKS_TON
• $GSL_CONST_MKS_METRIC_TON
• $GSL_CONST_MKS_UK_TON
• $GSL_CONST_MKS_TROY_OUNCE
• $GSL_CONST_MKS_CARAT
• $GSL_CONST_MKS_UNIFIED_ATOMIC_MASS
• $GSL_CONST_MKS_GRAM_FORCE
• $GSL_CONST_MKS_POUND_FORCE
• $GSL_CONST_MKS_KILOPOUND_FORCE
• $GSL_CONST_MKS_POUNDAL
• $GSL_CONST_MKS_CALORIE
• $GSL_CONST_MKS_BTU
• $GSL_CONST_MKS_THERM
• $GSL_CONST_MKS_HORSEPOWER
• $GSL_CONST_MKS_BAR
• $GSL_CONST_MKS_STD_ATMOSPHERE
• $GSL_CONST_MKS_TORR
• $GSL_CONST_MKS_METER_OF_MERCURY
• $GSL_CONST_MKS_INCH_OF_MERCURY
• $GSL_CONST_MKS_INCH_OF_WATER
• $GSL_CONST_MKS_PSI
• $GSL_CONST_MKS_POISE
• $GSL_CONST_MKS_STOKES
• $GSL_CONST_MKS_FARADAY
• $GSL_CONST_MKS_ELECTRON_CHARGE
• $GSL_CONST_MKS_GAUSS
• $GSL_CONST_MKS_STILB
• $GSL_CONST_MKS_LUMEN
• $GSL_CONST_MKS_LUX
• $GSL_CONST_MKS_PHOT
• $GSL_CONST_MKS_FOOTCANDLE
• $GSL_CONST_MKS_LAMBERT
• $GSL_CONST_MKS_FOOTLAMBERT
• $GSL_CONST_MKS_CURIE
• $GSL_CONST_MKS_ROENTGEN
• $GSL_CONST_MKS_RAD
• $GSL_CONST_MKS_SOLAR_MASS
• $GSL_CONST_MKS_BOHR_RADIUS
• $GSL_CONST_MKS_NEWTON
• $GSL_CONST_MKS_DYNE
• $GSL_CONST_MKS_JOULE
• $GSL_CONST_MKS_ERG
• $GSL_CONST_MKS_STEFAN_BOLTZMANN_CONSTANT
• $GSL_CONST_MKS_THOMSON_CROSS_SECTION
• $GSL_CONST_MKS_VACUUM_PERMITTIVITY
• $GSL_CONST_MKS_VACUUM_PERMEABILITY
• $GSL_CONST_MKS_DEBYE
• mksa - Standard MKSA system (meters, kilograms, seconds, amperes)
• $GSL_CONST_MKSA_SPEED_OF_LIGHT
• $GSL_CONST_MKSA_GRAVITATIONAL_CONSTANT
• $GSL_CONST_MKSA_PLANCKS_CONSTANT_H
• $GSL_CONST_MKSA_PLANCKS_CONSTANT_HBAR
• $GSL_CONST_MKSA_ASTRONOMICAL_UNIT
• $GSL_CONST_MKSA_LIGHT_YEAR
• $GSL_CONST_MKSA_PARSEC
• $GSL_CONST_MKSA_GRAV_ACCEL
• $GSL_CONST_MKSA_ELECTRON_VOLT
• $GSL_CONST_MKSA_MASS_ELECTRON
• $GSL_CONST_MKSA_MASS_MUON
• $GSL_CONST_MKSA_MASS_PROTON
• $GSL_CONST_MKSA_MASS_NEUTRON
• $GSL_CONST_MKSA_RYDBERG
• $GSL_CONST_MKSA_BOLTZMANN
• $GSL_CONST_MKSA_BOHR_MAGNETON
• $GSL_CONST_MKSA_NUCLEAR_MAGNETON
• $GSL_CONST_MKSA_ELECTRON_MAGNETIC_MOMENT
• $GSL_CONST_MKSA_PROTON_MAGNETIC_MOMENT
• $GSL_CONST_MKSA_MOLAR_GAS
• $GSL_CONST_MKSA_STANDARD_GAS_VOLUME
• $GSL_CONST_MKSA_MINUTE
• $GSL_CONST_MKSA_HOUR
• $GSL_CONST_MKSA_DAY
• $GSL_CONST_MKSA_WEEK
• $GSL_CONST_MKSA_INCH
• $GSL_CONST_MKSA_FOOT
• $GSL_CONST_MKSA_YARD
• $GSL_CONST_MKSA_MILE
• $GSL_CONST_MKSA_NAUTICAL_MILE
• $GSL_CONST_MKSA_FATHOM
• $GSL_CONST_MKSA_MIL
• $GSL_CONST_MKSA_POINT
• $GSL_CONST_MKSA_TEXPOINT
• $GSL_CONST_MKSA_MICRON
• $GSL_CONST_MKSA_ANGSTROM
• $GSL_CONST_MKSA_HECTARE
• $GSL_CONST_MKSA_ACRE
• $GSL_CONST_MKSA_BARN
• $GSL_CONST_MKSA_LITER
• $GSL_CONST_MKSA_US_GALLON
• $GSL_CONST_MKSA_QUART
• $GSL_CONST_MKSA_PINT
• $GSL_CONST_MKSA_CUP
• $GSL_CONST_MKSA_FLUID_OUNCE
• $GSL_CONST_MKSA_TABLESPOON
• $GSL_CONST_MKSA_TEASPOON
• $GSL_CONST_MKSA_CANADIAN_GALLON
• $GSL_CONST_MKSA_UK_GALLON
• $GSL_CONST_MKSA_MILES_PER_HOUR
• $GSL_CONST_MKSA_KILOMETERS_PER_HOUR
• $GSL_CONST_MKSA_KNOT
• $GSL_CONST_MKSA_POUND_MASS
• $GSL_CONST_MKSA_OUNCE_MASS
• $GSL_CONST_MKSA_TON
• $GSL_CONST_MKSA_METRIC_TON
• $GSL_CONST_MKSA_UK_TON
• $GSL_CONST_MKSA_TROY_OUNCE
• $GSL_CONST_MKSA_CARAT
• $GSL_CONST_MKSA_UNIFIED_ATOMIC_MASS
• $GSL_CONST_MKSA_GRAM_FORCE
• $GSL_CONST_MKSA_POUND_FORCE
• $GSL_CONST_MKSA_KILOPOUND_FORCE
• $GSL_CONST_MKSA_POUNDAL
• $GSL_CONST_MKSA_CALORIE
• $GSL_CONST_MKSA_BTU
• $GSL_CONST_MKSA_THERM
• $GSL_CONST_MKSA_HORSEPOWER
• $GSL_CONST_MKSA_BAR
• $GSL_CONST_MKSA_STD_ATMOSPHERE
• $GSL_CONST_MKSA_TORR
• $GSL_CONST_MKSA_METER_OF_MERCURY
• $GSL_CONST_MKSA_INCH_OF_MERCURY
• $GSL_CONST_MKSA_INCH_OF_WATER
• $GSL_CONST_MKSA_PSI
• $GSL_CONST_MKSA_POISE
• $GSL_CONST_MKSA_STOKES
• $GSL_CONST_MKSA_FARADAY
• $GSL_CONST_MKSA_ELECTRON_CHARGE
• $GSL_CONST_MKSA_GAUSS
• $GSL_CONST_MKSA_STILB
• $GSL_CONST_MKSA_LUMEN
• $GSL_CONST_MKSA_LUX
• $GSL_CONST_MKSA_PHOT
• $GSL_CONST_MKSA_FOOTCANDLE
• $GSL_CONST_MKSA_LAMBERT
• $GSL_CONST_MKSA_FOOTLAMBERT
• $GSL_CONST_MKSA_CURIE
• $GSL_CONST_MKSA_ROENTGEN
• $GSL_CONST_MKSA_RAD
• $GSL_CONST_MKSA_SOLAR_MASS
• $GSL_CONST_MKSA_BOHR_RADIUS
• $GSL_CONST_MKSA_NEWTON
• $GSL_CONST_MKSA_DYNE
• $GSL_CONST_MKSA_JOULE
• $GSL_CONST_MKSA_ERG
• $GSL_CONST_MKSA_STEFAN_BOLTZMANN_CONSTANT
• $GSL_CONST_MKSA_THOMSON_CROSS_SECTION
• $GSL_CONST_MKSA_VACUUM_PERMITTIVITY
• $GSL_CONST_MKSA_VACUUM_PERMEABILITY
• $GSL_CONST_MKSA_DEBYE
• math - Mathematical
• $M_E - Euler's Constant e
• $M_LOG2E - Log base 2 of e
• $M_LOG10E - Log base 10 of e
• $M_SQRT2 - Square root of 2
• $M_SQRT1_2 - Square root of 1/2
• $M_SQRT3 - Square root of 3
• $M_PI - Pi
• $M_PI_2 - Pi divided by 2
• $M_PI_4 - Pi divided by 4
• $M_SQRTPI - Square root of pi
• $M_2_SQRTPI - Two over the square root of pi
• $M_1_PI - One over pi
• $M_2_PI - Two over pi
• $M_LN10 - Natural log of 10
• $M_LN2 - Natural log of 2
• $M_LNPI - Natural log of pi
• $M_EULER - Euler-Mascheroni Constant
• num - Dimensionless Numbers
• $GSL_CONST_NUM_FINE_STRUCTURE
• $GSL_CONST_NUM_AVOGADRO
• $GSL_CONST_NUM_YOTTA
• $GSL_CONST_NUM_ZETTA
• $GSL_CONST_NUM_EXA
• $GSL_CONST_NUM_PETA
• $GSL_CONST_NUM_TERA
• $GSL_CONST_NUM_GIGA
• $GSL_CONST_NUM_MEGA
• $GSL_CONST_NUM_KILO
• $GSL_CONST_NUM_MILLI
• $GSL_CONST_NUM_MICRO
• $GSL_CONST_NUM_NANO
• $GSL_CONST_NUM_PICO
• $GSL_CONST_NUM_FEMTO
• $GSL_CONST_NUM_ATTO
• $GSL_CONST_NUM_ZEPTO
• $GSL_CONST_NUM_YOCTO
Importing the tag "all" is the same as importing all of these.
AUTHORS
Jonathan "Duke" Leto <jonathan@leto.net> and Thierry Moisan <thierry.moisan@gmail.com>
COPYRIGHT AND LICENSE
Copyright (C) 2008-2021 Jonathan "Duke" Leto and Thierry Moisan
This program is free software; you can redistribute it and/or modify it under the same
terms as Perl itself.