use strict;
use warnings;

my $ref_file = $ARGV[0];

if (isReadableFile ($ref_file)) {
  executeComm ("cat $ref_file");
} else {
  print STDERR "$ref_file Does not exist\n";
}

## In a different module...

sub isReadableFile {
  my $file = shift;

  if (defined ($file) &&             # was a file name passed?
      ((-f $file) || (-l $file)) &&  # is the file a file or sym. link?
      (-r $file)                     # is the file readable?
     ) {
    return 1;
  }
  else {
    return 0;
  }
}

sub executeComm {
  my ($comm) = @_;
  print "$comm\n";
  system ($comm);
  print "$?\n";
}