Your description doesn't completely tally with your code. If the file contains a single long string, then your while loop will only iterate once. However, to print out all, whitespace delimited words that either match or contain a given search term, you could use:

$string = 'this is a really long string (no really, it is!) that conta
+ins a whitespace delimited word';
print $1 while $string =~ m[(\b\S*limit\S*\b)]gi;; ## All words, case 
+insensitive.
delimited
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