in a perl script i m trying to run a command which invoke output from different server for that i have applied passwordless ssh. but in few machine it's not able to ssh and getting hung or prompting for password, it doesn't come out or go to next machine until i press enter. can anyone suggest something to overcome the issue.

Since you provide us with NO DETAILS at all, no, we can't really suggest much. You don't tell us anything about the version/distro of Linux, what you've done, post any of your code, etc.

Short answer: you're obviously having ssh issues between those machines...resolve it first, and put error handling routines in your code to resolve the isue.
Longer answer: you say "perl script", but don't post any of it. Are you using a system call to invoke ssh, or are you using a CPAN SSH perl module? If you're using a module, there are MANY, and all of them have error handling capabilities. Since you don't post your code, we don't know what you're doing, so can't really suggest anything.

thanks for the reply. i will try to work on error handling process.