The regexen we might build for that are neither unique nor equivalent to each other. If you want a regex that only matches something literal in the list,

my $re = do {
    local $" = '|';
    qr/^@{[map {quotemeta} @list]}$/;
};
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Automatically generated regexes are often inefficient or unwieldy in the interest of simpler generating code. Would you take qr/^[11111][22333][33333][44444][12312]$/ as a solution?

my @sets;
for (@list) {
    my $str = $_;
    for (0..(length-1)) {
        $sets[$_] .= substr $str, $_, 1;
    }
}
my $re = qr/^${\join '', map {"[$_]"} @sets}$/;
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This is a pretty open-ended problem. You should look carefully at what you expect from your data and what kind of solution you want.

Update: If the real problem is to construct an efficient test of whether a string is in @list, use a hash:

{
    my %test_hash;
    @test_hash{@list} = ();
    sub efficient_test { exists $test_hash{+shift}; }
}
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