#! /usr/local/bin/perl -w      # 1
                               # 2
use strict;                    # 3
                               # 4
my $foo = shift || 'ok';       # 5
my $bar; # = undef             # 6
                               # 7
print "foo contains [$foo]\n"; # 8
if( $foo eq 'nok' ) {          # 9
    print "foo is nok\n";      # 10
}                              # 11
elsif( $bar eq 'rat' ) {       # 12
    print "bar is rat\n";      # 13
}                              # 14
else {                         # 15
    print "nothing\n";         # 16
}                              # 17

##</code><code>##

foo contains [ok]
Use of uninitialized value in string eq at ifbug line 9.
nothing

##</code><code>##

awk -F: 'substr($1,0,1)=="p" {print $3}' /etc/passwd
perl -F: -lane 'substr($F[0],0,1)eq"p" and print $F[2]' /etc/passwd