Then check that $b has a value. You could just use $b as the test, ie. 
if( $b and $a =~ /$b/ ) { do this }

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but I wouldn't do that in case $b == 0. I also wouldn't use eq in case $b is numeric or == in case $b is a string. So do something like,
if ($b !~ /^$/ and $a =~ /$b/) { do this }

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In reply to Re: Don't want to match nothing by Adam
in thread Don't want to match nothing by Anonymous Monk

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