Transfer the file, but do not overwrite it. When your program notices that a new version has arrived, it writes its current state out to harddisk and runs the updater, which just switches the files around. 
#!/usr/bin/perl
# 529755.pl

use strict;
use diagnostics;

my $importantdatatomangle = 1;

sub checkfornew {
    my $newversionfilename    = '529755.pl.newversion';
    if (
        -e $newversionfilename    # does the new file exist?
        and
        (time - (stat $newversionfilename)[9] > 2)
        # is it older than 2 sec, i.e. has it been completely
        # transferred to this here box?
    ) {
        # save the current state of the program out to harddisk
        # i.e. $importantdatatomangle
    # ...
        warn "found a new version, running updater";
        exec 'perl updater.pl' or die "could not exec updater: $!";
        # run the updater
        # see perldoc -f exec why I included error checking
    };
};

# main program starts below here
while (1) { # loop for "many hours", actually forever :p
    {
        # do important work
        $importantdatatomangle    = -$importantdatatomangle;
        warn "data is now $importantdatatomangle";
        sleep 5;
        warn "zzzzz";
    };
    checkfornew;    # periodically check for newer version
};

[download]
Actually you have to read the current state from harddisk back into your variables at the very beginning of the program. I'm just setting my variable to 1 out of laziness. 
#!/usr/bin/perl
# updater.pl

use strict;
use diagnostics;

use File::Copy;

# improve this shoddy programming,
# remember to actually check the return values of move for errors

move '529755.pl', '529755.pl~';            # create backup
move '529755.pl.newversion', '529755.pl';    # deploy new version

warn "deployed new version, going to run it now";
exec 'perl 529755.pl' or die "could not exec new version: $!";

[download]
Next time on perlmonks, show what you have programmed so far, or else you get slapped with a wet octopus.

In reply to Re: Restart Long Running Perl Script by Anonymous Monk
in thread Restart Long Running Perl Script by avo

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