Here is my dilemma:

I need to search for the phrase: !CCSD(T) STATE 1.1 ENERGY in a text file.

simply enough, I can use the matching operator as such:
$_ =~ m/'!CCSD\(T\) STATE 1.1 ENERGY'/
The string is matched and all is well.

The complication comes in because I need to read the phrase from a different text file. Once the phrase is parsed from the text, I store it in a variable called $flag.

I, then, use the matching operator this way:
$_ =~ m/$flag/
The string never matches.

I have tried every conceivable combination of quotes and backslashes without any luck. How can I get this rather seemingly routine thing to work?

In reply to string matching by Anonymous Monk

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