If your abc program is perl also, use <STDIN> explicitly; not <>. In what follows echo.pl is your abc. kprasanna.pl is the script calling it.

echo.pl:

use strict;
use warnings;

my $arg = $ARGV[0];
my $line = <STDIN>;              # bare <> won't work
print "argument was $arg\ninputline was $line";
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kprasanna.pl:

use strict;
use warnings;

my $file = $ARGV[0];
system "./echo.pl $file";
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Running it:

duper:~/pp carol$ ./kprasanna.pl a_filename
hello kprasanna                  # typed in at terminal
argument was a_filename
inputline was hello kprasanna
duper:~/pp carol$
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Hope it helps.