Hello editholla,

I haven’t studied your code in detail, but this section leaps to the eye:

#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})/){
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That regex will match any sequence of 5 digits beginning with a 4. However, the comment suggests you need this:

/(4\d{3}[a-z]/i
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but that will also match a substring as part of a longer string. Is that what you intended? If not, add word boundary assertions:

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