Analysis of A highly valuable chain of thoughts

HAD cigarettes no ashes,
                 And roses ne'er a thorn,
             No man would be a funker
             Of whin, or burn, or bunker.
             There were no need for mashies,
                 The turf would ne'er be torn,
             Had cigarettes no ashes,
                 And roses ne'er a thorn.

Had cigarettes no ashes,
                 And roses ne'er a thorn,
             The big trout would not ever
             Escape into the river.
             No gut the salmon smashes
                 Would leave us all forlorn,
             Had cigarettes no ashes,
                 And roses ne'er a thorn.

But 'tis an unideal
                 Sad world in which we're born,
             And things will 'go contrairy'
             With Martin and with Mary:
             And every day the real
                 Comes bleakly in with morn,
             And cigarettes have ashes,
                 And every rose a thorn.