You will have to "feed" the value of the variable to the recursion, e.g. using a command-line argument.

use strict;
my $temp = shift @ARGV || 0;
print "call no. $temp\n";
if ( $temp < 10 )
{
    system ("rec.pl", $temp+1);
}
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This will print

call no. 0
call no. 1
call no. 2
call no. 3
call no. 4
call no. 5
call no. 6
call no. 7
call no. 8
call no. 9
call no. 10
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