There are inconstancies between your input and output data. I can't determine the rule for handling white space so you will have to figure that much out for yourself.

The key to your main problem is split. Something like:

    my ($first, @fields) = split ';', $line;
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splits the string in $line into a number of elements in a list then assigns the first element to $first with the rest ending up in @fields.

Note that we like to see what you have tried and like to be told if you are working on homework so that we can tailor our help to your situation.

thank you so much for the instruction

use warnings;
use strict;

while (<>) {
    chomp;
    my ($name,@rest)= split(/\s*;\s*/,$_);
    foreach (@rest) {
    print $name,'; ',$_,"\n";
    }
}
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this will print the result to the screen, but if you call this script with

thisscript old.txt > new.txt
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the output gets stored in the file new.txt. Or you can change the script to explicitly open a file with the open() function and print to it

It works. Thank you very much. Glad to attend this great perl family.

#!/usr/bin/perl

use strict;

while (<DATA>) {
    chomp;
    my $name;
    s/^(\w+)\s?;// and $name = $1;
    for my $i ( split ";" ) {
        print "$name; $i\n";
    }
}

__DATA__
alex ;teacher; 1945-12-1; california
john; lawyer ; texas
peter ;teacher; 1948-01-04
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