i read that using grep is not advisable for huge files

Someone lied to you.

You probably want something like this: 

while ( <FILE> ) {
    print if 'abc' eq ( split /:/ )[ 0 ];
}

[download]

Or possibly this: 

while ( <FILE> ) {
    print if /^abc:/;
}

[download]

In reply to Re: find a string and count of its occurence in a text file by Anonymous Monk
in thread find a string and count of its occurence in a text file by new@perl

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