Try this. '<:raw' is roughly equivalent to binmode. The unpack templates: 'A100' tells it to treat the first 100 bytes as a null terminated string; 'i'(*) means treat the next 4 bytes as a signed integer.

#! perl -slw
use strict;

open IN, '<:raw', $ARGV[ 0 ] or die $!;
my $binary = do{ local $/; <IN> }; ## read the whole file
close IN;

my( $name, $roll_no, $grade ) = unpack 'A100 i i', $binary; 

print "name: $name; no:$roll_no; grade:$grade";

__END__
C:\test>junk58 Myfile
name: myname; no:149; grade:1
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(*If the data is read on a different hardware platform from that where it is written you may need to change the 'i' template.)