I always start with use strict;, but still I have problems with lexical variables scoped outside of subroutines. Here is some simple code which demonstrates the problem: 
use strict;

my $fn="myfile";
print readfile($fn);

sub readfile
{
  my $out="";
  open(FH, $fn) or die "Can't read $fn";
  $out .= $_ while(<FH>);
  return $out;
}

[download]

I meant to use $fn as passed to the subroutine, but strict didn't help me catch my mistake.

Here is the improved version: 

use strict;

{
  my $fn="myfile";
  print readfile($fn);
}

sub readfile
{
  my $out="";
  open(FH, $fn) or die "Can't read $fn";
  $out .= $_ while(<FH>);
  return $out;
}

[download]
In the improved version, strict catches the mistake. The improvement is to write { } around code outside the subs.

This helps me with debugging, especially casual programs.

It should work perfectly the first time! - toma

In reply to Improving lexical scoping outside subs by toma

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