Perl detects undeclared subs (which is better than detecting undefined subs) at compile-time if you omit parens on sub calls. 

>perl -c -e"use strict; sub f {} f;"
-e syntax OK

>perl -c -e"use strict; sub f;   f;"
-e syntax OK

>perl -c -e"use strict;          f;"
Bareword "f" not allowed while "strict subs" in use at -e line 1.
-e had compilation errors.

>perl -c -e"use strict; sub g {}  g 'abc';"
-e syntax OK

>perl -c -e"use strict;           g 'abc';"
String found where operator expected at -e line 1, near "g 'abc'"
        (Do you need to predeclare g?)
syntax error at -e line 1, near "g 'abc'"
-e had compilation errors.

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Omitting parens on sub calls causes a whole of weird stuff, so I recommend against doing this.

In reply to Re: Detecting undefined subroutines at compile time by ikegami
in thread Detecting undefined subroutines at compile time by bdenckla

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