So in both perl and javascript you can use the same algorithm if you'd like.

Start with an arrary with all of your breakpoint values. I'll abridge here.

var breakpoints = [ 25000 , 50000 , 150000 ]; 
my @breakpoints = ( 25000 , 50000 , 150000 );
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Then push the new value in. For our example I'll push in 50123.

 
breakpoints.push(50123);
push(@breakpoints, 50123);
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Sort them. Do an index-of on your value - 1.

breakpoints.sort();
var return_value = breakpoints[breakpoints.indexOf(50123) - 1];

@breakpoints = sort @breakpoints;
# Use your favourite perl method for indexOf like above
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In javascript this is actually cleaner than perl. The sort in javascript doesn't have to do a copy at the end and it has the 'indexOf' operator built in. </code>