use strict;

# Put some phrases in an array for us to test
my @phrases = (" APIblahblah", "blah APINblah", "blahUWI     .");

# Match on each phrase
my $phrase;
foreach $phrase (@phrases) {

	# Do a match - note the brackets around the entire expression.
	# Brackets are used as a memory
	# See a Regular Exp guide for more info
	if ($phrase =~ m/(\bAPI|APIN|UWI\s*\.)/) {
	
		# If it matched we are here... $1 prints the memory of what
		# matched inside the brackets. Similarly if there was a
		# 2nd set of parentheses $2 would contain their match etc.
		print "Phrase: $phrase, matched on: $1\n";
	
		# Rather than printing it here you could call your sub...
		# e.g.
		
		# somesub($1);
	}
}