I'm assuming you searched CPAN and noone made a portable solution. That means you'll need to get the info from the system, but you didn't specify your OS.

That said, I'm also very curious as to why you need the start time of some arbitrary process.

Update: Hum, you didn't look on CPAN, I'd say. In a few seconds, I found

• Win32::Process::Info
• Win32::Process::Info::NT
• Win32::Process::Info::PT
• Win32::Process::Info::WMI
• BSD::Process
• Sys::Statistics::Linux::Processes
• Proc::ProcessTable
• Surely more!

The last even appears to be a portable solution!

You might start with On asking for help and How do I post a question effectively?.

Then, having internalized those, perhaps Super Search or Tutorials would help, and then perhaps Learning Perl

perldoc: perlvar - Search for $PID or $$

perldoc: time

Not what you need most likely, but gotta be with the above poster in asking what you have tried thus far?

use strict;
use warnings;

my $launch_time   =  time();
# Do something with $launch_time

# execute external
my $result = qx!/some/program -flags!;
# Check for success

# or

#exec and exit
{ exec ('/some/program') }; print STDERR "couldn't exec program: $!";
# if exec fails, this script continues
$launch_time      = 'LAUNCH_FAILED';
[download]

As fidesachates suggested, if you are on Linux, you could try parsing the time output of ps like this.

perl -we 'use Date::Manip::Date; my $pid = shift; my $sstart = readpip
+e("TZ=UTC ps --no-headers --format lstart --pid " . (0+$pid)); my $st
+art = Date::Manip::Date->new($sstart, [SetDate => "zone,UTC"]); my $e
+start = $start->printf("%s"); print "process $pid started at epoch ti
+me $estart\n";' 1967
[download]

Alternately let's skip running ps and emulate what it does (except that it actually obtains the Hertz value in a different way).

perl -we 'use POSIX(); my $pid = shift; my $seconds_since_boot; { open
+ my $UPTIME, "<", "/proc/uptime" or die; <$UPTIME> =~ /(\S+)/ or die;
+ $seconds_since_boot = 0+$1; } my $start_time; { open my $STAT, "<", 
+"/proc/" . (0+$pid) . "/stat" or die; <$STAT> =~ /\)(.+)/ or die; $st
+art_time = 0+(split " ", $1)[19]; } my $Hertz = POSIX::sysconf(POSIX:
+:_SC_CLK_TCK()); my $start_epoch = time() - $seconds_since_boot + $st
+art_time / $Hertz; print "process $pid started at epoch time $start_e
+poch\n"' 1967
[download]

Note that this may have up to one second of error.

One would think this problem has an easier solution, and maybe someone else will show one, but I couldn't get anything simpler than this.

Update 2012-04-13: a somewhat related later question is A regular expression that will work for (hh:)mm:ss [converting clock time to seconds].

pid=12345
ps -o etime= "$pid"
[download]

You would simply need to set this environment variable system-wide (in /etc/profile) or in the user's individual profile file to cause an idle login session to be terminated after a specified amount of seconds:

# Set TMOUT to 15 minutes, read-only so user cannot override it.
TMOUT=900
readonly TMOUT
export TMOUT
[download]

Niël