my ($sec,$min,$hour,$mday,$mon,$year,
     $wday,$yday,$isdst)=localtime(time);

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The time keyword returns an integer value of seconds since epoch... if you decrement that value before sending it to localtime you can return any date/time you want. I.e :

my $week_of_seconds = 60 * 60 * 24 * 7;

my $current_time = time();

my $week_ago = $current_time - $week_of_seconds;

my ($sec,$min,$hour,$mday,$mon,$year,
     $wday,$yday,$isdst)=localtime($week_ago);

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The above isn't tested because I can't be bothered, the solution looks more or less like that, play around with it.

use DateTime qw();
my $now             = DateTime->now;
my $previous_monday = $now->subtract(days => ($now->wday_0 || 7));
my $formatted_date  = $previous_monday->ymd(q());   # 20111114
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My preferred Swiss Army Knife for date-handling is Date::Calc. It offers Monday_of_Week, which you can use after identifying the week using Week_of_Year.

Thank you very much! That helped me a lot, but i'm still struggeling with for formatting of the outputtet date, i have read and tried messing with the 'ymd' parameter without any luck

Scratch that, did'nt look properly on your snippet, sorry. But thanks

use Date::Manip;
print ParseDate("last Monday");
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ZRTM (The RTM, The Read The Manual, TRTM sounds farty)

last monday

The date last monday

A Better Way To Get Days Since Monday of Last Week

Hmm, too specific, last day

How to get last day of 2 months ago

Calc last friday of month

Determining the dayname for the last day of any given month

Calculating latest 'Sunday' date on the first of the month

What is the best way to get a list of all Mondays until the end of the year?

Yeah, DateTime is great

Fav’d.

Remember ... this is Perl ... and we don’t actually use the language (just) because we love the punctuation.   :-D   We do it for CPAN, which at this immediate moment has:

73,482 Uploads; 23,767 Distributions; 101,586 Modules; 9,348 Uploaders.

... and by the time you read this, those numbers probably will have increased again.

So, no matter what it is you’re doing, it has already been done.   That realization should guide your every thought and your every move.   Perl has one of the largest and the most mature libraries of ruggedly-tested code out there, anywhere.   So, if you want a new door, you don’t pick out a tree and buy a sawmill ... you pick out a door that suits you (they’re all free ...), and you install it.   Done.   If you’ve got a problem, you select a solution to that problem and install it.   Done.

#!/usr/bin/perl
use strict;
use warnings;
use POSIX qw/ strftime /;

# Script to get prior Monday (if today is Mon, then Mon a week ago).

print scalar localtime, "\n", last_monday(localtime);

sub last_monday {
    my ($wday, @dmy) = @_[6, 3..5];
    
    # (will work across month, year boundries)
    $dmy[0] -= ($wday+6) % 7 || 7; # $dmy[0] == mday
    return strftime "%Y%m%d000000", 0,0,0,@dmy;
}
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PS: Ratazong's suggestion implicitly offers an algorithm to avoid the problem above: Identify week number of current week and of the previous Monday... and if those are the same, adjust Monday_of_Week as required.

PPS: Christoforo's reply has a solution, too.