To run script in debug mode you should add -d option in the command line:
$perl -d script.pl
If t is specified, it indicates to the debugger that threads will be used in the code being debugged:
$perl -dt script.pl
Additional info at perldocperlrun
$perl -d:MOD script.pl runs the program under the control of a debugging, profiling, or tracing module installed as Devel::MOD.
For example, -d:NYTProf executes the program using the Devel::NYTProf profiler.
See all available Devel modules here
Recommended modules:
Devel::NYTProf -- Powerful fast feature-rich Perl source code profilerDevel::Trepan -- A modular gdb-like Perl debuggerDevel::MAT -- Perl Memory Analysis ToolDevel::hdb -- Perl debugger as a web page and REST serviceDevel::DebugHooks::KillPrint -- Allows to forget about debugging by print statementDevel::REPL -- A modern perl interactive shellDevel::Cover -- Code coverage metrics for Perl