I made some improvements on the program, so it will handle the command line arguments and it will show the parent filename at each node. And there is no need to generate a PS image.

#!/opt/csw/bin/perl -
# Author : Rob G, The Netherlands
#          Based on script by: Valter Mazzola, txian@hotmail.com, Ital
+y
# Date   : 24/May/2012

# Purpose:
# ---> Generate a Graph-ical call tree for your *.pm perl module files
+.
# gra.pl assumes that:
# 1- you have defined sub(s) with  'sub myfunc {' with 'sub' at the be
+ginning of line.
# 2- you call your sub with the '&' and brackets, i.e.  &my_sub ();

# usage: 
# 1) generate the .dot text graph file definition  
#    perl gra.pl *.pm > myfile.dot
# 2) generate the graph using 'dot' executable ( http://www.research.a
+tt.com/sw/tools/graphviz/ )
#    dot -Tjpg myfile.dot -o myfile.jpg
# 3) display the graph
#    JPG viewer  

use File::DosGlob;

my $fc = 1; # a file counter to distingguish between multiple main-fil
+es

# first expand the command line arguments
@ARGV = map {
  my @g = File::DosGlob::glob($_) if /[*?]/;
  @g ? @g : $_;
} @ARGV;

# then loop through all files and exclude myself from the loop
for my $file (@ARGV) {
  if ($file ne $0) {
    open(my $fh, $file) or die "Can't open $file: $!\n";
    $cur_sub = "main".$fc; # used to show the parent of main subs
    $fc++;
    while (<$fh>) {
      if (/^sub\s+(.*?)\s*\{/) {
        $cur_sub = $1;
        $modules{$cur_sub} = $file;    
      }
      if (/\&([\d\w_]+)\s*\(/){
        $c_sub = $1;
        $n = 0;
        foreach $k (@{$called_subs{$cur_sub}}) {
          if ($c_sub eq $k) {
            $n = 1;
            last;
          }
        } 
        if ($n == 0) {
          push @{$called_subs{$cur_sub}}, $c_sub;
          $modules{$cur_sub} = $file;    
        }
      }
    }
    close $fh;
  }
}

print "digraph G {\n";
print "   page=\"44,68\";\n";                       # make sure the gr
+aph is large enough
print "   ratio=auto;\n";
print "   rankdir=LR;\n";                           # ) I prefer porta
+it
print "   orientation=portrait;\n";                 # )
print "   node[fontsize=10,fontname=\"Arial\"]\n";  # and another font
+name, fontsize

# first we define the label and shape of each node
# the label is contructed from the name of the sub and the name of the
+ parent file
# the shape for the main entries is different from the other nodes
#
# a side-effect: it will show all sub's that are not used too
while (($key, $value) = each (%modules)) {
  if (substr($key, 0, 4) eq "main") {
    print "   $key [shape=ellipse,label=\"main\\n($value)\"];\n";
  } else {
    print "   $key [shape=box,label=\"$key\\n($value)\"];\n";
  }
}

# then we define the paths between the nodes
foreach $k (keys(%called_subs)) {
  $ref_arr = $called_subs{$k};
  if (ref($ref_arr)) {
    foreach $y (@{$ref_arr}){
      print "   $k -> $y;\n";
    }
  }
}

print "}\n";
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