And btw, that regex is not bulletproof. "foo and exit" and a whole bunch of other nasties could slip by.

Incorrect. Not unless \w has suddenly started to match spaces rather than just [A-Za-z0-9_]. Please show me *ANY* nasty that will pass through. Without spaces, && || ; , etc you have no statement separator you can get into that eval to let you add to the require.

my @nasties = (
    'foo and exit',
    "foo\nand\nexit\n",
    "hello",
    "foo\000exit",
);

for my $layer(@nasties) {
    print $layer =~ m/^([\w:]+)$/ ? "OK $layer\n" : "ERR $layer\n";
}
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