#!/usr/bin/perl -w
use strict;

use Time::HiRes qw[ time ];

# OP: "I have a perl script that I need to run 1000 times and for each run 
#      I need to store how much time it took to run... "
# using foo_a.pl, execute this from foo_a's dir
# Timings of foo_a.pl are NOT precise because they include the time 
# to execute the calculations here.

my $begin = time;
for my $arg( 1..1000 ) {
	my $start = time;
	system "perl foo_a.pl $arg";
	my $duration = (time - $start);
    print "\n\t\$arg: $arg, \t\$start: $start, \t\$duration: $duration\n";
	$start = time;
}

print "$begin" . time . "\n";
exit;

##</code><code>##

#! /usr/bin/perl -w
use strict;

#foo_a.pl

print "--foo_a.pl's marker inserted when run at LN11 in 1173964_a.pl: ";
exit;

##</code><code>##

--foo_a.pl's marker inserted when run at LN11 in 1173964_a.pl: 
	$arg: 1, 	$start: 1476409956.16692, 	$duration: 0.0165810585021973
--foo_a.pl's marker inserted when run at LN11 in 1173964_a.pl: 
	$arg: 2, 	$start: 1476409956.18353, 	$duration: 0.0134079456329346
--foo_a.pl's marker inserted when run at LN11 in 1173964_a.pl: 
	$arg: 3, 	$start: 1476409956.19695, 	$duration: 0.0137300491333008
--foo_a.pl's marker inserted when run at LN11 in 1173964_a.pl: 
	$arg: 4, 	$start: 1476409956.2107, 	$duration: 0.0142498016357422

# elided for brevity and henceforward, "marker inserted" lines deleted:

	$arg: 495, 	$start: 1476409962.28221, 	$duration: 0.0129170417785645
	$arg: 496, 	$start: 1476409962.29514, 	$duration: 0.0133938789367676
	$arg: 497, 	$start: 1476409962.30855, 	$duration: 0.0117459297180176
	$arg: 498, 	$start: 1476409962.32031, 	$duration: 0.0139508247375488
	$arg: 499, 	$start: 1476409962.33427, 	$duration: 0.0135560035705566
	$arg: 500, 	$start: 1476409962.34784, 	$duration: 0.0124979019165039
	$arg: 501, 	$start: 1476409962.36035, 	$duration: 0.0137338638305664
	$arg: 502, 	$start: 1476409962.3741, 	$duration: 0.0120208263397217
	$arg: 503, 	$start: 1476409962.38613, 	$duration: 0.0119149684906006
	$arg: 504, 	$start: 1476409962.39807, 	$duration: 0.0124168395996094
	$arg: 505, 	$start: 1476409962.4105, 	$duration: 0.0128791332244873

# another long stretch omitted...

	$arg: 995, 	$start: 1476409968.50899, 	$duration: 0.0113530158996582
	$arg: 996, 	$start: 1476409968.52035, 	$duration: 0.0118088722229004
	$arg: 997, 	$start: 1476409968.53218, 	$duration: 0.011375904083252
	$arg: 998, 	$start: 1476409968.54356, 	$duration: 0.0114960670471191
	$arg: 999, 	$start: 1476409968.55507, 	$duration: 0.0122640132904053
	$arg: 1000,     $start: 1476409968.56735, 	$duration: 0.0137550830841064