#Find all instances of specific five character strings 
#starts with 4, then 3 more numbers, then a letter)
chomp $line;
if ($line =~ /(4\d{4})/){

##</code><code>##

/(4\d{3}[a-z]/i

##</code><code>##

/\b(4\d{3}[a-z])\b/i