You wouldn't use substr to generate an err msg. You'd check length of whatever variable shouldn't be too long, and if it exceeded your limit, you'd have the program die or just not call the code that inserts the information into your data store, and generate a page that informs the user that the data they entered was rejected. 
if (length($var) > 30) {
  # Generate rejection message
}
else {
  # Insert data
  # Generate success message
}

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In reply to Re^7: Tweak for my Perl Regex that screens for digits only by Roy Johnson
in thread Tweak for my Perl Regex that screens for digits only by hackermike

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