What should happen if you run the script on Sat or Sun?

my @Now = localtime(time);
print "Today: $Now[3] - $Now[6]\n";
my $Mon = time - (86400 * ($Now[6] - 1));
my @Monday = localtime($Mon);
print "Monday: $Monday[3] - $Monday[6]\n";
my $Fri = $Mon + (86400 * 4);
my @Friday = localtime($Fri);
print "Friday: $Friday[3] - $Friday[6]\n";
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Explanation:

Get the splitted time values for now - returns the day of week as 6 starting with 0 for sunday

Monday is today - (seconds_per_day * (day_of_week - ))

Friday is 5 days after monday

This won't work in the following cases:

On the two change days for daylight saving there is a one hour for each day where the next day is not 86400 seconds away.

There has been a time (and there will be a time) where some days were skipped to match the calendar to the earth/sun relation.

You could advoid this by using localtime to get the current days values and step back (and forward) day-by-day by using timelocal(0,0,0,day,month,year) - 1 or timelocal(59,59,23,day,month,year) + 1 until you reach a monday or friday, but usually the above sample is accurate enough.