my $secret="(binary garbage here)";
sub checkSecurity;
sub decodeSecret;
sub reencode;
if (checkSecurity()) {  # <--- bypass the function call or make the function return TRUE
    my $plaintext=decodeSecret($secret);
    # breakpoint here
    say $plaintext;
    # or, if you like:
    say reencode($plaintext);
} else {
    die "Insecure condition found, won't tell you the secret!\n";
}

##</code><code>##

package DBIspy;

use strict;
use warnings;
use feature 'say';
use DBI;

no warnings 'redefine';
sub DBI::connect
{
        say for @_;
        die 'BROKEN';
}
1;

##</code><code>##

> perl -MDBIspy -E 'use DBI; DBI->connect("dbi:SQLite:","user","password")'
DBI
dbi:SQLite:
user
password
BROKEN at DBIspy.pm line 12.

>