glob() *expands* wildcards, but if there's no wildcard it leaves them alone, in just the same way as the shell does:

$ echo $SHELL # yes, this is important!
/bin/bash
$ ls
foo1  foo2  foo3
$ echo foo*
foo1 foo2 foo3
$ echo foo
foo
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There's a difference however, if you specify a wildcard that doesn't match anything:

$ echo bar*
bar*
$ perl -e 'print glob("bar*")'
$
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This is because glob() uses csh semantics:

$ csh
% ls
foo1  foo2  foo3
% echo bar*
echo: No match.
% echo bar*
echo: No match.
% perl -e 'print glob("bar*")'
%
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