use strict;
use warnings;

my $str = $ARGV[0];

if ($str =~ /^[a-zA-Z0-9]{6,20}$/) {
   print "success!\n";
} else {
   print "failure\n";
}

[download]

A bit shorter.

Scott

In reply to Re: how should i test whether a string contains between 6 and 20 letters and numbers by helphand
in thread how should i test whether a string contains between 6 and 20 letters and numbers by keiusui

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