perl -d:DProf foo.pl

##</code><code>##

perl -MDevel::Profiler foo.pl

##</code><code>##

dprofpp

##</code><code>##

main();

sub main {
    my $now = time();
    for( my $x = 0; $x <= 1_000_000; $x++ ) {
        print scalar localtime, "\n" if $now != time();
        $now = time();
    }

    return;
}

##</code><code>##

Total Elapsed Time = 1.859881 Seconds
  User+System Time = 1.389881 Seconds
Exclusive Times
%Time ExclSec CumulS #Calls sec/call Csec/c  Name
 98.5   1.370  1.370      1   1.3700 1.3700  main::main
 0.72   0.010  0.010      2   0.0050 0.0050  main::BEGIN

##</code><code>##

main();

sub main { all_the_work() }

sub all_the_work {
    my $now = time();
    for( my $x = 0; $x <= 1_000_000; $x++ ) {
        print scalar localtime, "\n" if $now != time();
        $now = time();
    }

    return;
}

##</code><code>##

Total Elapsed Time = 1.809848 Seconds
  User+System Time = 1.379848 Seconds
Exclusive Times
%Time ExclSec CumulS #Calls sec/call Csec/c  Name
 98.5   1.360  1.360      1   1.3600 1.3600  main::all_the_work
 0.00       -  1.360      1        - 1.3600  main::main
 0.00       -  0.010      2        - 0.0050  main::BEGIN

##</code><code>##

main();

sub main {
    do_nothing();
    all_the_work();
}

sub do_nothing { sleep 5 }

sub all_the_work {
    my $now = time();
    for( my $x = 0; $x <= 1_000_000; $x++ ) {
        print scalar localtime, "\n" if $now != time();
        $now = time();
    }

    return;
}

##</code><code>##

Total Elapsed Time = 6.809867 Seconds
  User+System Time = 1.459867 Seconds
Exclusive Times
%Time ExclSec CumulS #Calls sec/call Csec/c  Name
 97.9   1.430  1.430      1   1.4300 1.4300  main::all_the_work
 0.68   0.010  0.010      2   0.0050 0.0050  main::BEGIN
 0.00       - -0.000      1        -      -  main::do_nothing
 0.00       -  1.430      1        - 1.4300  main::main

##</code><code>##

Total Elapsed Time = 6.799829 Seconds
         Real Time = 6.799829 Seconds
Exclusive Times
%Time ExclSec CumulS #Calls sec/call Csec/c  Name
 73.5   5.000  5.000      1   5.0000 5.0000  main::do_nothing
 26.1   1.780  1.780      1   1.7800 1.7800  main::all_the_work
 0.15   0.010  0.020      2   0.0050 0.0100  main::BEGIN
 0.00       -  6.780      1        - 6.7800  main::main