In an eval evironment in which @_ was, e.g.,
@_ = ('searchPattern', 'replacementString', 'regexModifiers');
(presumably, the eval statement is called in the context of a function to which arguments were passed via @_), the eval would return a code reference equivalent to
sub { s/searchPattern/replacementString/regexModifiers for @_ }
which would allow one to iterate over a list of strings and do substitutions on each (non-literal!) string:
my $x = 'some';
my $y = 'strings';
my $z = 'here';
$sub->($x, $y, $z);
The only benefit that I can see of using the string eval is that the regex | substitution operator modifiers /g /e /r and perhaps a couple others cannot be "passed" in any other way. If not for these modifiers, one could simply write something like (again, assuming this is in a function in which @_ held search/replace strings)
my $sub = sub { s/$_->[0]/$_->[1]/xmsg for @_ };
...
$sub->($x, $y, $z);
(note the literal modifier group) and get the same result. In this example, the modifiers other than /g could be passed in a string.
Update: E.g.,
c:\@Work\Perl\monks>perl -wMstrict -le
"S('(?xmsi) foo', 'bar', 'g');
;;
sub S {
my $sub = eval qq{ sub { s/$_[0]/$_[1]/$_[2] for \@_ } };
;;
my $x = 'foo';
my $y = 'Foo fOo foO';
my $z = 'FOO';
;;
$sub->($x, $y, $z);
print qq{x '$x' y '$y' z '$z'};
}
"
x 'bar' y 'bar bar bar' z 'bar'
And yes, this is a trick for a completely trusted environment. But then: "Trust, but
verify!"
Give a man a fish: <%-{-{-{-<