Uhm, this problem has been solved decades ago. Unix comes with a large set of utilities. One doesn't have to remember where a particular utility is located - that's why you have a PATH environment variable. One doesn't have to remember what the parameters of a utility are, that what manual pages and usage messages are for. One doesn't even have to remember which utility does what, that's what apropos is for - and that will even show you which Perl modules to use.

$ apropos localtime
localtime [ctime]    (3)  - transform date and time to broken-down tim
+e or ASCII
timegm               (3)  - inverses for gmtime and localtime
Time::localtime      (3pm)  - by-name interface to Perl's built-in loc
+altime() function
timelocal [timegm]   (3)  - inverses for gmtime and localtime
Time::tm             (3pm)  - internal object used by Time::gmtime and
+ Time::localtime
$
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Abigail