The fact that you said "match" sounds like you're talking about a regular expression... is that the case? If so, you can just say

if ($var =~ /bob/i) {
    # Bob matches bob
}
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Or, as the previous poster said, if you're just trying to compare two strings case-insensitively, use

if (lc $var eq "bob") {
    # Bob matches bob
}
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