There are a number of modules that return an absolute path without resolving anything.

use Path::Tiny qw( path );
my $abs = path($0)->absolute;
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For example, launching the script using ./a.pl or perl a.pl from /home/ikegami/foo would result in /home/ikegami/foo/a.pl.

But note that launching the script using ../bar/a.pl or perl ../bar/a.pl from /home/ikegami/foo would result in /home/ikegami/foo/../bar/a.pl. That's because /home/ikegami/foo/../bar/a.pl can't be safely reduced to /home/ikegami/bar/a.pl because /home/ikegami/foo might be a symlink.