As indicated by the first reply, a single regex consisting of 100 values as alternates is not such a big load, really. And you don't even need a special module to do it this way:

my $value_regex = join( '|', values %msgDefn );  # actually, use anony
+monk's version below...

while ( <FILEHANDLE> ) {
    print if ( /$value_regex/ );
}
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That assumes that the values in your hash are all "safe", in the sense that they don't contain any regex magic characters, like brackets, *, ?, +, period, slash, backslash, and so on.

If the values might contain things of that sort, you could handle it like this (but YMMV, depending on what's really in your data):

my $value_regex = join( '|', map { '\Q'.$_.'\E' } values %msgDefn );
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Now, if you ultimately need to know which hash key contains the value that actually matched a given line from the file, then you'd really want to build a reverse hash, as suggested in the 2nd reply.

Update (forgot to mention): Naturally, lots of other caveats apply, such as false-alarm matches on substrings (e.g. a value like "table", treated as above or as in the OP, would match on a line that contains "stable" or "tablet", which might not be what you want.