Provided by: groff_1.23.0-3build2_amd64 bug

Name

       gperl - execute Perl commands in groff documents

Synopsis

       gperl [file ...]

       gperl -h
       gperl --help

       gperl -v
       gperl --version

Description

       This is a preprocessor for groff(1).  It allows the use of perl(7) code in groff(7) files.  The result of
       a Perl part can be stored in groff strings or numerical registers based on the arguments at a final  line
       of a Perl part.

       If  no  operands  are  given,  or  if  file is “-”, gperl reads the standard input stream.  A double-dash
       argument (“--”) causes all subsequent arguments to be interpreted as file operands, even if  their  names
       start  with  a  dash.   -h  and  --help display a usage message, whereas -v and --version display version
       information; all exit afterward.

Perl regions

       Perl parts in groff files are enclosed by two .Perl requests with different arguments, a starting and  an
       ending command.

   Starting Perl mode
       The starting Perl request can either be without arguments, or by a request that has the term start as its
       only argument.

              •      .Perl.Perl start

   Ending Perl mode without storage
       A .Perl command line with an argument different from start finishes a running Perl part.  Of  course,  it
       would be reasonable to add the argument stop; that's possible, but not necessary.

              •      .Perl stop.Perl other_than_start
       The  argument other_than_start can additionally be used as a groff string variable name for storage — see
       next section.

   Ending Perl mode with storage
       A useful feature of gperl is to store one or more results from the Perl mode.

       The output of a Perl part can be got with backticks `...`.

       This program collects all printing to STDOUT (normal standard output) by the Perl  print  program.   This
       pseudo-printing  output  can have several lines, due to printed line breaks with \n.  By that, the output
       of a Perl run should be stored into a Perl array, with a single line for each array member.

       This Perl array output can be stored by gperl in either

       groff strings
              by creating a groff command .ds

       groff register
              by creating a groff command .rn

       The storage modes can be determined by arguments of a final stopping .Perl command.   Each  argument  .ds
       changes  the mode into groff string and .nr changes the mode into groff register for all following output
       parts.

       By default, all output is saved as strings, so .ds is not really needed before  the  first  .nr  command.
       That  suits to groff(7), because every output can be saved as groff string, but the registers can be very
       restrictive.

       In string mode, gperl generates a groff string storage line
              .ds var_name content
       In register mode the following groff command is generated
              .nr var_name content

       We present argument collections in the following.  You can add as first argument for all stop.   We  omit
       this additional element.

       .Perl .ds var_name
              This  will  store  1 output line into the groff string named var_name by the automatically created
              command
                     .ds var_name output

       .Perl var_name
              If var_name is different from start this is equivalent to the former command, because  the  string
              mode is string with .ds command.  default.

       .Perl var_name1 var_name2
              This  will  store  2  output  lines  into  groff string names var_name1 and var_name2, because the
              default mode .ds is active, such that no .ds argument is needed.  Of course, this is equivalent to
                     .Perl .ds var_name1 var_name2
              and
                     .Perl .ds var_name1 .ds var_name2

       .Perl .nr var_name1 varname2
              stores both variables as register variables.  gperl generates
              .nr var_name1 output_line1
              .nr var_name2 output_line2

       .Perl .nr var_name1 .ds var_name2
              stores the 1st argument as register and the second as string by
              .nr var_name1 output_line1
              .ds var_name2 output_line2

Example

       A possible Perl part in a roff file could look like that:
              before
              .Perl start
              my $result = 'some data';
              print $result;
              .Perl stop .ds string_var
              after

       This stores the result ”some data” into the roff string called string_var, such that the  following  line
       is printed:
              .ds string_var some data
       by gperl as food for the coming groff run.

       A Perl part with several outputs is:
              .Perl start
              print ”first\n”;
              print ”second line\n”;
              print ”3\n”;
              .Perl var1 var2 .nr var3
       This  stores 3 printed lines into 3 groff strings.  var1,var2,var3.  So the following groff command lines
       are created:
              .ds var1 first
              .ds var2 second line
              .nr var3 3

Authors

       gperl was written by Bernd Warken ⟨groff-bernd.warken-72@web.de⟩.

See also

       Man pages related to groff are groff(1), groff(7), and grog(1).

       Documents related to Perl are perl(1), perl(7).