Indeed, the idiomatic expression is rather

 
while( m/REGEX/g ) {
    ... # use groups only if match successful 
}
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The only reason to check $2 separately, is to make sure it's not false ( "", 0, undef, etc )

this can be done with

while( m/REGEX/g ) {
    last unless $2;
    ...  
}
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tho I doubt the OP is aware of all those false cases.