#!/bin/perl -w use strict; my $file= shift or die "usage $0 "; open( FILE, "<$file") or die "cannot open $file: $!"; while( my $device_id= ) { chomp $device_id; # removes the end of line unless( $device_id=~ /^\d{10}$/) { die "invalid device id: $device_id"; } # do your stuff here }